Hansgrohe Citerio M - Leak Problem Resolution needed !

4 Houses in This estate have all same units fitted,and 3 so far encountered the same problem,the houses are under 5 years old(New Built),so the units too.
My Customer have replaced the cartridge previously with no improvement in the leak or prevention
With this unit
www.divapor.co...
The neighbour have replaced it with a genuine unit supplied and fitted from Hansgrohe fitter which lasted 3 months and start leaking again,
Now this wont be just a money pit game and must have a logical explanation and solution,
Se Hansgrohe please Provide a Logical solution to this problem so I can rectify that in all 3 houses and possibly in the 4th one when the time comes.
The link for the units My customers believe are fitted :
www.axor-desig...
Will be waiting for a resolution ASAP as the water wont stop.